Concentration of barite



Patented Mar. 13, 1928.

UNITED STATES PATENT OFFICE.

WALTER O. BOBCHERDT, OF MOUNTAIN LAKES, NEW JERSEY, ASSIGNOR TO THE NEW JERSEY ZINC COMPANY, OF NEW YORK, N. Y., A. CORPORATION OF NEW JERSEY.

CONCENTRATION OF 'BARITE.

No Drawing.

This invention relates to theconcentration of barite from barite ores or other halite-bearing material, and has for .its obiect the provision of an improved process for concentrating barite by selective frothtlotation.

Barite is rather unique among the min- :rals in that for most of its applications an extremely high degree of purity of the concentrate is required. Lump barite is ordinarily notmarketable if it contains less than 58% BaSO,, and in some markets a barium sulfate content of less than 92% is not desired. There are both technical and economic reasons for this situation. Some of the common impurities of barite act not only as diluents, causing a degradation of the material, but also have a positive deleterious action because of their influence in the further processes of treatment to which the material is subjected or upon the final product in which the barite is used.

Barite is a relatively soft and friable mineral and in grinding therefore tends to grind finer under given conditions than many of the minerals with which it is associated. Since in ordinary gravity concentration of minerals, sliming is to be special; ly avoided because of the (lifiiculty of hantiling the extremely fine-size mineral parholes in grav ty concentrating machines, illllS characteristic of the mineral'operates commercially to inhibit concentration below a certain range of particle size. It, therefore, has been and is now customary, in the practice of gravity concentration methods, to discard certain products during the concentration of barite ore,'despite the fact that they contain a considerable quantity of barite, since the cost of recovering thisbarite outweighs the possible profit from the operation; in part for the reason before stated, and in part because the impurities with which the barite is associated often have: a specific gravity so close to that of the 'barite itself as to render gravity concentration diflicult and uneconomlcal.

The present invention contemplates the concentration of barite by froth-flotation.

In carryingout the invention the baritebearing material is subjected to froth-fiotation' in the presence of v a barite-selective flotation agent, thereby effecting a substantial concentration of the baribe in the result- Application filed October 19, 1927. Serial No. 227,363.

ing overflow froth. More particularly, the

invention contemplates the provision of a barite under proper conditions of applica- 1 tion. Cotton seed oil pitches are by-prodnets of the refining of cotton seed oil and they may be obtained commercially in three forms, known respectively as soft, medium and hard pitch. Soft pitch is a liquid; mediumpitch is a stiff paste-like substance; and hard pitch is a solid tar-like substance. The soft pitch is slightlyn'iiscible in water when heated, and, while it produces some froth when added directly to the flotation cell, it

cannot be conveniently used in that manner. The medium and hard pitches are almostentirely immiscible inavatei', even when heated. I have'found that when these substances are used as flotation reagents in solution in asoline,they give excellent results in barlte flotation. The gasoline possesses some frothingower, but by itself does notyield a sat-1s actory grade of .concentrate, The cotton seed. oil pitches, when dissolved in gasoline yield copious froths and appear to have a high degre'eof selective power for barite.

It is well known that certain colloidal constituents of pie pulps are prejudicial or inhibitory to the flotation of sulfids and I have found, likewise, that when barite ores are ground to a size which renders them convenient for treatment by froth-flotation, there generallyexists in the pulp colloidal matter which is prejudicial to securing the maximum grade of barite concentrate, the maximum recovery of barite, or both, by froth-flotation.

A large proportion of the barite o're at present mined in the United States is derived from so-calle'd residual deposits, and since the gangue in which the barite nodules of such ores occur is principally clay and earth, it will be understood that barite ores derived fromthis source contain an unusual amount of colloidal matter.

Barite ores derived from vein 'or bedded deposits do not generally contain as much colloidal matter as those derived from residual" deposits, but in the line grinding of barite ores to the degree required to produce suitable conditions for froth-flotation of the barite, there is almost invariably produced or released a sufficient amount of colloidal material to exercise a deleterious effect upon the froth-fiotation treatment of the barite.

In some cases, as where the ore contains a relatively small amount of colloids, it may be sufficient, in order to secure good results, to bring about the defiocculation or dispersion of such colloids preliminarily to flotation, but ordinarily, better results can be secured in all cases by deflocculating and then decanting at least a part of the colloidal constituents associated with the barite ore pulp before the ore is subjected to frothtiotation treatment.

In connection with thepreliminary removal of colloids in the concentration of barite ores in order to secure the particularly high grade concentrates which are called for by the barite-consuming trade, the disclosures of my United States Patents No. 1,448,515, dated March 13, 1923, and No. 1,454,838, dated May 8, 1923, are of particular value and importance.

Since barite is a relatively soft and brittle mineral, I find that in barite-bearing log washer tailings, and similar products, and in barite ore pulps which have been ground to a degree suitable to prepare them for flotation, that often considerable of the barite itself becomes colloidal within the meaning which I have assigned to that term in my aforementioned United States pateuts,.to wit, The colloidal matters may be present as pure colloids, organic or inorganic, or in a state bordering on the so-called coarse suspensions.

Throughout this specification and the appended claims, I intend to embrace in the expressions colloids, colloidal slimcs. and colloidal constituents, both true colloids and those quasi or borderland substances which may not be truly colloidal but partake of the qualities of, or resemble, colloids, and without regard to the sources from which such colloidal matters are derived. Thus, for the purpose ofthe present invention, the colloidal constituents may be considered as ranging from just above the molecular size upward through the class of so-called suspensoids. which, while possibly not true colloids, still, because of their relatively large specific surface, exhibit some, if not all of-the properties (if colloids, and are capable of existing in both the sol or gel state,

or of being dispersed and coagulated or flocculated and defiocculatcd. By a colloidal slime, therefore, I mean a material which is not necessarily a true colloid, but which exhibits colloidal characteristics to a sufiicient degree to make it amenable to the mauipulation herein described.

Some of the barite itself generally exists in a colloidal condition in the flotation pulp, and I have found that even when the pulp contains a minimum of other colloidal con stituents it is generally desirable. to preliminarily remove colloidal constituents, including colloidal barite, before subjecting the barite-bearing ore pulp to froth-flotation treatment, for the reason that colloidal barite floats with extreme case and it. therefore, tends to unduly armor or coat the bubbles of the froth, producing a condition geucrall v known as over-stabilization. This condition of over-stabilization, regardless of whether it is brought about by baritc or by other colloidal constituents, is an objcctioir able condition because it tends to mechanically entangle or entrain gangue particles, and to carry them over. into the concentrate.

It will be clear from this discussion that in the flotation of barite, colloidal constituents may in several different ways exert a deleterious or undesirable ellcct. (iangue colloids tend to pass into the froth, thus contaminating the concentrate directly, by reducing its-grade, and indirectly by creating over-stabilization of the froth and thus further reducing the concentrate grade by carrying over gangue particles. Such colloids also often exert a direct inhibitory uction on the flotation of the coarser particles of barite, causing them to tend to rcnu"u in the tailing, thus reducing the rccoviry of barite. Colloidal barite, while perhaps not in any way interfering with the recovery, does tend, by over-stabilization of the froth, to carry over gangue particles which should remain in the tailing.

The process of defiocculatiou and decantation, by which the colloidal constituents are in part separated from the ore pulp,

depends upon the. fact that by dispersing and deflocculating such colloidal constituents thev can be held in suspension in quiet pulp. That is, that they can be given a practically zero settling rate. whilst the noncolloidal constituents of the pulp are permitted to settle. In the practice of the process, when sedimentation of the non-colloidal particles has progressed sufficiently, the bulk of the liquid, containing the suspended colloidal constituents and small amounts of extremely fine slow settling non-colloidal constituents, is decanted from the sediment, as described in detail in my United States patents to which reference has been made.

In the case of barite ores, the colloid suspension is often of such character and quansolids contained in such a decanted suspension may thus be separated and recovered from the water 1n whlch they are suspended by flocculatmg them with appropriate agents and permitting them to settle in the form of a mud or sludge. Or they may be flocculatcd and separated from the bulk of the water with which they are associated by a frothflotation treatment, according to the process described in my United States Patent 1,445,989. The solids may be recovered from the aforementioned sludge. or from the colloid-bearing froth Just referred to, by vacu um filtration, or by evaporation of water, or by a combination of these two means.

In carrying out my laboratory tests, in cases where no removal of the colloidal constituents of the ore was conducted, I ground a one kilogram (dry weight) sample of the ore in a laboratory ballmill until it was reduced to the desired degree of fineness. I then diluted the sample with water so that the pulp contained about 5 parts of water to 1 part of ore by weight and placed this pulp in a laboratory flotation machine, or cell, of the pneumatic type.

The pulp having been placed in the rougher cell, the desired kind and quantity of flotation reagent was added and air was bubbled through the porous blanket, forming with the flotation agent, a baritebearing froth which was permitted to overflow gently, thus removing the flotable mineral. From time to time samples of the tailing were \\-'ithd ra\\'n from-the cell for examination and returned through the feed pipe, and the liquid coming over with the concentrate froth was separated at intervals and. returned to the cell through the feed pipe, thus maintaining a practically constant dilution within the cell and returning part of the flotation agent which was used repeatedly. Further additions offresh flotation agent were made if and when required and a run was considered complete when the froth no longer contained any considerable quantitv of the flotalole mineral and when .the tailings appeared to be relatively free of such mineral. At this point, the material remaining in the cell was removed and evaporated to dryness. this residue forming the tailing from the test. The concentrate was diluted, as required, and placed in the cleaner cell. additional flotation agent being added, if necessary. At the first pass of the cleaner a cleaner concentrate was made, the material remaining in the cell at the end of the run constituting middling which was removed and evaporated to dryness. The cleaner concentrate was replaced in the cleaner cell, diluted with water as required, additional flotation agent' added necessary and again frothed to produce the final or re-cleaner concentrate which was evaporated to dryness, whilst the material remaining in the cell, known as the second or re-cleaner? middling was added to' the first or clcaner middling and evaporated to dryness.

\Vhen it was desired to deflocculate the colloidal constituents of the ore pulp, I added an appropriate deflocculating agent, generally sodium silicate, either to the pulp before it was ground in the laboratory ball mill or the pulp which was ready for flotation, just enough of the sodium silicate or other deflocculating agent being used to secure the desired result. The deflocculated pulp was then placed in the rougher cell and treated as above described.

lVhen I desired to remove a portion of the colloid content of the ore, I generally added the required amount of sodium silicate or other deflocculating agent to the ore in the laboratory ball mill, thus grinding'the ore in the presence of the deflocculating agent. lVhen the ore was ground to the desired fineness, I diluted with water. forming a pulp in which the colloids were deflocculated. This pulp was allowed to stand quietly in tall cylinders for several hours'or until the greater part of the non-colloidal portion of the pulp had settled out. The supernatant colloid-bearing liquor was then carefully decanted. The settled material was re-pulped with an appropriate quantity of water and, 1f necessary, an additional amoimt. of deflocculat-lng agent was added. These steps were ltit) repeated until thecolloid content of the pulp had been reduced to the desired extent, which was indicated by experiment, whereupon the final residue was diluted with water and placed in the flotation machine as previously described, while the colloid-bearing liquid, which had been decanted in the several steps above mentioned, was evapo rated to dryness. It will thus be seen that starting with a dry weight of one kilogram of feed sample of known composltion, I recovered a concentrate, a middling and a tailing product, or a colloid, a concentrate, amiddling. and a'tailing product from each test. Each of these products was evaporated. to drvness, weighed and analyzed. and from the figures .so obtained, the grade and recovery were calculated.

From many similar amples are selected as representatives of the results which may be obtained by practice of the preferred form of the process of the present invention. j j g EwampZe I.-Using 25 cc. of a solution of cotton seed oil hard pitch, 10 grams dissolved tests, the following ex- TJI . Per cent i Per cent Grams Per k l Grams of mm Baso. Basso. g gj t Calculated analysis of frrd sample. Actual analysis of fwd sample.

lLlra'mp/e l[.In another test, using 25 cc. of a solution of cotton seed oil hard pitch, 1 grain dissolved in 50 cc. of gasoline, or at the rate of 1 pound of hard pitch and 6 gallons of gasoline per ton of material treated, and a feed sample containing 62.61% BaSO and ground to pass 80 mesh, :1 barite concentrate containing 97.61% Babt), was obtained with a recovery of 68.60% of the barite contained in the original "feed sample.

Eamnpie [[[.In another test, using 10 cc. of a solution of cotton seed oil medium pitch, 5 grams dissolved in 50 cc. of gasoline, or at the rate of 2 pounds of medium pitch and 2.4 gallons of gasoline per ton of material treated, and a feed sample containing 56.5070 BaSO, and ground to pass 80 mesh, a barite com'entratc containing 96.60% BaSO, was obtained with a recovery of 69.20% of the barite contained in the original feed sample.

Ewample ]V.-In another test, using 7 cc. of a solution of cotton seed oil soft pitch, 5 grams dissolved in 50 cc. of gasoline, or at the rate of 1.4 pounds of soft pitch and 1.68 gallons of gasoline per ton of material treated, and a feed sample containing 56.50% BaSO, and ground to pass 80 mesh, a barite concentrate containing 97.30% BaSO, was obtained with a recovery of 78.10% of the barite contained in the original feed sample.

In its commercial application, the process of the present invention may be carried out in standard froth-flotation machines, either of the so-called agitation type, or of the socalled pneumatic type, or in the machines which represent a combination of the principles of the two preceding types. I prefer to use the pneumatic type machines because of the great capacity which it is pomibleto secure from a given size machine, and the greater ease of regulation and control. But, as usual in the treatment of minerals by flotation, certain circumstances connected with the ore, the location of the mill, the cost of power and of skilled attendance often indicate some one type of flotation apparatus fl being better suited to the situation than others.

I have found that the degree of comminution to which the barite ore must be subjected to fit it for froth-flotation recovery of its barite content does not differ greatly from that to which sulfid ores intended for flotation are ordinarily reduced. In any event, the ore must be ground fine enough to secure effective severance of the diverse minerals which it contains, and, in general, it is not practicable to float material coarser than that which will pass 35 mesh Tyler standard sieve. lVorking with a sample of barite bearing jig tailing from a barite concentrating plant located at Cartersville, Georgia, with which all the conditions of experiment were kept as nearly as practicable indentical, except that the degree of comminution of ore was varied, I foundthat the degree of comminution in this case, where minerals are practically free from attachment to one another at 35 mesh, had practically no hearing upon the results which could be secured.

I have found that in barite flotation, the considerations respecting dilution of the pulp are the same as they are in the flotation of sulfids. The degree of dilution will depend upon the character of the ore, the fineness of grinding, and similar considerations. Only rarely is the dilution greater than six weights of water per weight of ore, or less than three weights of water per weight or ore. Dense pulp generally gives greater capacity to the flotation machines, but might make it more diflicult to secure high grade concentrate and usually a smaller quantity of flotation agent suflices with a dense than with a more dilute pulp.

Barite flotation, according to the process of the present invention. may be carried on in acid, neutral or alkaline pulps, but, because of the wider choice of reagents for deflocculation and flotation which that renders available, it is usually preferable to conduct the flotation in a neutral or alkaline pulp. When, because of other circumstances, such as the natural acidity of the mine water, it is desirable to conduct the flotation on an acid pulp, certain modifications may be necessary if it should be impracticable to neutralize the acidity of the'pulp, as by the use of lime.

As is commonly the practice in the flotation of sulfids, it may,'in the case of certain barite ores, be necessary to employ certain addition agents for the purpose of properly conditioning the pulp. Thus, it

may be necessary to add lime, or some other alkali, to overcome acidity, or sodium Slllcate, gum arable, trisodium phosphate, or

some similar agent, to secure or maintain V grinding arative tests, as will be understood by those pkilled in the art to which this invention reates. The temperature of the barite-bearing flotation pulp may, if, necessary, be varied as by coo in the pulp by dilution with cold water or v passing it over cooling towers, or by heating it,-as by the introduction of steam; but on the score of cost, it is generally desirable to conduct flotation at the'natural temperature of the mill water, and, generally, other factors afiecting vthe flotation can be controlled so as ,to permit of this.

In'the practice of the'process of the inlvention, keeping in mind the necessity for producing very high grade concentrate with a maximum recovery at the lowest possible cost for investment and operation, tests should be made oneach ore which it is desired to treat, in order to determine the optimum conditions relating to degree of of the ore, deflocculation, or removal of colloids, neutrality, alkalinity or barlte ore dress ng can acidity of the pulp, the degree of dilution of the pulp, and its temperature, theagent or agents to be used for conditioning the pulp and securing the barite flotation, and the type of flotation machine.

By means of the precess of the present invention, it is possible to produce very high grade barite concentrates with a high percentagerecovery of the barite contalned 1n the ore, thus making it possible to improve the rade of barite ores which are now marketa iile, but whose value can be further improvin their grade. Ores not heretofore amenab e to commercial exploitationcan be economically treated for the recovery of-their barite content, and waste roducts of present gravity methods of be reclaimed and retreated. a

w I claimrfl a 1.-The method of concentrating baritebearing material which comprises subjecting the barite-bearing materialin the form of a pulp to a froth flotation operation in the presence of cotton seed oil pitch.

2. The methodlof concentratirtg bariteb'earing material which comprises a ding cotton seed oil pitch dissolved in an appropriate solvent to a pulp of the barite-bearing material, and thereafter subjecting the pulp to a froth flotation o ration.

3. The meth enhanced by in the of concentrating h itebearing material which comprises adding cotton seed oil itch dissolved in gasoline to a pulp of the arite-bearing material, and thereafter subjecting the pulp to a froth flotation operation. p

4. The method of concentrating baritebearing material associated with flocculated colloidal matter in a pulp, dispersing or deflocculating the colloidal matter, and thereafter subjecting the pulp to a froth flotation operation in the presence of cotton seed oil pitch. -5. The method of concentrating baritebearing material which comprises grinding the barite-bearing material to flotation size in the presence of sodium silicate, and thereafter subjecting froth flotation operation in the presence of cotton seed oil pitch.

6. The method bearing material matter in a pulp,

associated with colloidal which comprlses removing colloidal matter from the pulp, and there-' to a froth flotation after subjecting the pulp operation in the presence pitch. Y

7 The method of concentrating bariteof cotton seed oil bearing material associated with flocculated WlllCll com rises colloidal matter in a pulp, dispersing or deflocculating the col oidal matter, treating the pulp to remove the disof concentrating barite-.

which comprises the ground material to a ersed colloidal matter, and thereafter subecting the oration in pitch 8. bearing material associated with flocculated colloidal matter in a pulp,

ul'p to a froth flotation .op-

the presence OfCOttOII seed 011.

he method of concentrating 'barit-ewhich comprises dispersin or deflocculatmg the colloidal matter, su jecting the resulting pulp to sedimentation and decantation for the removal of colloidal matter, and thereafter subjecting the pulp to afroth flotation operation in the presence of cotton seed oil pitch.

- 9. The method of.- concentrating baritebearing material which comprises, grinding the barite-bearing resence of water and sodium silicate, subjectmgthe resulting pulp to sedimentation' and decantation for the separation and removal of colloidal materialfand subjecting the remaining pulp to a fr'oth flotation operation in the presence of cotton seed oilpitch.

In testimony whereof I aflix my signature.

0.v BORCHERDT.

material to flotation size: 

